According to WHO statistics on blood safety, 80 percent of the world's population has access to 20 percent of the world's safe blood supply. However, more than 20 percent (13,000,000 units) of the world blood supply is not tested for the three major transfusion-transmissible infections: HIV, HBV and HCV. Transfusion of unsafe blood accounts for 8-16 million hepatitis B virus infections. If inexpensive, rapid, improved dipsticks with sensitivity comparable to EIA were developed for blood screening, it would greatly improve the safety of the blood supply in developing countries.The overall aim of the project is to develop a HBsAg dipstick assay with high sensitivity, designated as the reflex diagnostic. The test can be used in developed countries under circumstances where an immediate result is required. For the developing countries, we propose that this test be integrated into a triplex test (HBV, HIV & HCV) and used as the initial step of pre-donation screening in high prevalence countries. The associated second step is to use the HBsAg reflex diagnostic test in order to identify the agent responsible for the positive Triplex test result.The specific aims of Phase I are to optimize the reagents in order to produce a prototype with sub-nanogram sensitivity and to evaluate the assay in 50 HBV-positive samples.